Tubular patent foramen ovale (pfo) closure device with catch system

ABSTRACT

The present invention provides a device for occluding an anatomical aperture, such as an atrial septal defect (ASD) or a patent foramen ovale (PFO). The occluder includes two sides connected by a central tube. The occluder is formed from a tube, which is cut to produce struts in each side. Upon the application of force, the struts deform into loops. The loops may be of various shapes, sizes, and configurations, and, in at least some embodiments, the loops have rounded peripheries. In some embodiments, at least one of the sides includes a tissue scaffold. The occluder further includes a catch system that maintains its deployed state in vivo. When the occluder is deployed in vivo, the two sides are disposed on opposite sides of the septal tissue surrounding the aperture and the catch system is deployed so that the occluder exerts a compressive force on the septal tissue and closes the aperture.

FIELD OF THE INVENTION

The present invention relates generally to an occlusion device for theclosure of physical anomalies, such as an atrial septal defect, a patentforamen ovale, and other septal and vascular defects.

BACKGROUND OF THE INVENTION

A patent foramen ovale (PFO), illustrated in FIG. 1, is a persistent,one-way, usually flap-like opening in the wall between the right atrium11 and left atrium 13 of the heart 10. Because left atrial (LA) pressureis normally higher than right atrial (RA) pressure, the flap usuallystays closed. Under certain conditions, however, right atrial pressurecan exceed left atrial pressure, creating the possibility that bloodcould pass from the right atrium 11 to the left atrium 13 and bloodclots could enter the systemic circulation. It is desirable that thiscircumstance be eliminated.

The foramen ovale serves a desired purpose when a fetus is gestating inutero. Because blood is oxygenated through the umbilical chord, and notthrough the developing lungs, the circulatory system of the fetal heartallows the blood to flow through the foramen ovale as a physiologicconduit for right-to-left shunting. After birth, with the establishmentof pulmonary circulation, the increased left atrial blood flow andpressure results in functional closure of the foramen ovale. Thisfunctional closure is subsequently followed by anatomical closure of thetwo over-lapping layers of tissue: septum primum 14 and septum secundum16. However, a PFO has been shown to persist in a number of adults.

The presence of a PFO is generally considered to have no therapeuticconsequence in otherwise healthy adults. Paradoxical embolism via a PFOis considered in the diagnosis for patients who have suffered a strokeor transient ischemic attack (TIA) in the presence of a PFO and withoutanother identified cause of ischemic stroke. While there is currently nodefinitive proof of a cause-effect relationship, many studies haveconfirmed a strong association between the presence of a PFO and therisk for paradoxical embolism or stroke. In addition, there issignificant evidence that patients with a PFO who have had a cerebralvascular event are at increased risk for future, recurrentcerebrovascular events.

Accordingly, patients at such an increased risk are considered forprophylactic medical therapy to reduce the risk of a recurrent embolicevent. These patients are commonly treated with oral anticoagulants,which potentially have adverse side effects, such as hemorrhaging,hematoma, and interactions with a variety of other drugs. The use ofthese drugs can alter a person's recovery and necessitate adjustments ina person's daily living pattern.

In certain cases, such as when anticoagulation is contraindicated,surgery may be necessary or desirable to close a PFO. The surgery wouldtypically include suturing a PFO closed by attaching septum secundum toseptum primum. This sutured attachment can be accomplished using eitheran interrupted or a continuous stitch and is a common way a surgeonshuts a PFO under direct visualization.

Umbrella devices and a variety of other similar mechanical closuredevices, developed initially for percutaneous closure of atrial septaldefects (ASDs), have been used in some instances to close PFOs. Thesedevices potentially allow patients to avoid the side effects oftenassociated with anticoagulation therapies and the risks of invasivesurgery. However, umbrella devices and the like that are designed forASDs are not optimally suited for use as PFO closure devices.

Currently available septal closure devices present drawbacks, includingtechnically complex implantation procedures. Additionally, there are notinsignificant complications due to thrombus, fractures of thecomponents, conduction system disturbances, perforations of hearttissue, and residual leaks. Many devices have high septal profile andinclude large masses of foreign material, which may lead to unfavorablebody adaptation of a device. Given that ASD devices are designed toocclude holes, many lack anatomic conformability to the flap-likeanatomy of PFOs. Thus, when inserting an ASD device to close a PFO, thenarrow opening and the thin flap may form impediments to properdeployment. Even if an occlusive seal is formed, the device may bedeployed in the heart on an angle, leaving some components insecurelyseated against the septum and, thereby, risking thrombus formation dueto hemodynamic disturbances. Finally, some septal closure devices arecomplex to manufacture, which may result in inconsistent productperformance.

The present invention is designed to address these and otherdeficiencies of prior art septal closure devices.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a device for occluding anaperture in septal tissue, including a first side adapted to be disposedon one side of the septal tissue and a second side adapted to bedisposed on the opposite side of the septal tissue. The first and secondsides are adapted to occlude the aperture upon deployment of the deviceat its intended delivery location. The device also includes a catchsystem that maintains the configuration of the device once it has beendeployed.

According to some embodiments, the catch system reduces and maintainsthe axial length of the device. Also, varied constructions could be usedto maintain the axial dimension of the device. In one form, catchelements such as, e.g., balls, attached to a delivery wire could be usedto maintain the axial dimension of the device. In a differentconstruction, a locking mechanism could be used. Preferably, if alocking mechanism is used, it secures both sides of the device in thelocked position with a single locking element.

According to at least some embodiments, the device is formed from atube. According to some embodiments, the tube includes a materialselected from the group consisting of metals, shape memory materials,alloys, polymers, bioabsorbable polymers, and combinations thereof. Inparticular embodiments, the tube includes a shape memory polymer.According to some embodiments, the device is formed by cutting the tube.

According to some embodiments, at least one of the first and secondsides of the device includes a tissue scaffold. According to someembodiments, the tissue scaffold includes a material selected from thegroup consisting of polyester fabrics, Teflon-based materials,polyurethanes, metals, polyvinyl alcohol (PVA), extracellular matrix(ECM) or other bioengineered materials, synthetic bioabsorbablepolymeric scaffolds, collagen, and combinations thereof. In particularembodiments, the tissue scaffold includes nitinol.

According to some embodiments, the first and second sides of the deviceare connected by a central tube. According to some embodiments, thecentral tube is positioned so as to minimize distortion to the septaltissue surrounding the aperture. In particular embodiments, the centraltube is positioned at an angle θ from the second side, and the angle θis greater than 0 degrees and less than about 90 degrees.

In another aspect, the present invention provides a device for occludingan aperture in septal tissue, including a first side adapted to bedisposed on one side of the septal tissue and a second side adapted tobe disposed on the opposite side of the septal tissue. The first andsecond sides are adapted to occlude the defect when the device isdeployed at its intended delivery location. Each of the first and secondsides includes loops. The device further includes a catch system thatmaintains the configuration of the device once it has been deployed. Theloops of the first and second sides and the catch system cooperate toprovide a compressive force to the septal tissue surrounding theaperture.

According to some embodiments, each of the first and second sidesincludes at least two loops. In particular embodiments, each of thefirst and second sides includes four or six loops. Of course, the mostdesirable number of loops on each side will depend on a variety ofanatomical and manufacturing factors.

According to some embodiments, the device also includes a central tubethat connects the first and second sides. According to some embodiments,the central tube is positioned so as to minimize distortion to theseptal tissue surrounding the aperture. In particular embodiments, thecentral tube is positioned at an angle θ from the second side, and theangle θ is greater than 0 degrees and less than about 90 degrees.

According to some embodiments, the device is formed from a tube.According to some embodiments, the tube includes a material selectedfrom the group consisting of metals, shape memory materials, alloys,polymers, bioabsorbable polymers, and combinations thereof. Inparticular embodiments, the tube includes nitinol. In particularembodiments, the tube includes a shape memory polymer.

According to some embodiments, at least one of the first and secondsides further includes a tissue scaffold. According to some embodiments,the tissue scaffold includes a material selected from the groupconsisting of polyester fabrics, Teflon-based materials, polyurethanes,metals, polyvinyl alcohol (PVA), extracellular matrix (ECM) or otherbioengineered materials, synthetic bioabsorbable polymeric scaffolds,collagen, and combinations thereof. In particular embodiments, thetissue scaffold includes nitinol.

According to some embodiments, each of the loops includes a rounded edgeat its periphery to minimize trauma to the septal tissue. In particularembodiments, the outer periphery of the device is circular.

In still another aspect, the present invention provides a method ofmaking a device for occluding an aperture in septal tissue, includingproviding a tube having first and second ends and upper and lowerportions, cutting at least four axially-extending openings in the upperportion of the tube, cutting at least four axially-extending openings inthe lower portion of the tube. The openings in the upper and lowerportions are separated by a central portion of the tube.

According to some embodiments, the tube includes a material selectedfrom the group consisting of metals, shape memory materials, alloys,polymers, bioabsorbable polymers, and combinations thereof. Inparticular embodiments, the tube includes a shape memory polymer.

In yet another aspect, the present invention provides a method ofoccluding an aperture in septal tissue, including providing a tubehaving first and second ends and upper and lower portions in a deliverysheath. The tube includes at least four axially-extending openings inits upper portion and at least three axially-extending openings in itslower portion. The openings in the upper and lower portions areseparated by a central portion of the tube. The deliver sheath isinserted into a right atrium of a heart, through the aperture in theseptal tissue, and into the left atrium of the heart. The first end andthe upper portion of the tube are deployed into the left atrium. Thesheath is then retracted through the aperture and into the right atriumof the heart, where the second end and the lower portion of the tube aredeployed into the right atrium. The sheath is then withdrawn from theheart. Of course, a catch system could be used to secure the device in adelivered (expanded) state. The catch system may have any or all thecharacteristics described in the specification. Further, other types ofcatch systems could be used to hold the device in the delivered state.

According to some embodiments, a force is applied to each of the firstand second ends in an axial direction such that the axial length of thetube is reduced. The force applied to the first end is in a directionopposite to that of the force applied to the second end.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a human heart including variousseptal defects;

FIGS. 2A-2D are isometric views of an embodiment of an occluderaccording to the present invention;

FIGS. 3A-3C are front elevational, side, and cross-sectional views,respectively, of the occluder of FIGS. 2A-2D;

FIGS. 4A-4B are front elevational and side views, respectively, ofanother embodiment of an occluder according to the present invention;

FIGS. 5A-5B are front and side views, respectively, of still anotherembodiment of an occluder according to the present invention;

FIGS. 6A-6E are isometric views of one embodiment of a catch systemaccording to the present invention;

FIGS. 7A-7C are side views of another embodiment of a locking mechanismaccording to the present invention;

FIGS. 8A-8C are isometric views of yet another embodiment of an occluderaccording to the present invention;

FIGS. 9A-9H are side views of one method for delivering an occluderaccording to the present invention to a septal defect; and

FIGS. 10A-10D are side views of one method for retrieving an occluderaccording to the present invention from a septal defect

FIGS. 11A-11C are isometric views of occluders according to variousembodiments of the invention;

FIGS. 12A and 12B are side and top views, respectively, of an alternateembodiment of an occluder according to the present invention;

FIG. 13 is a side view of an embodiment of the occluder of the presentinvention; and

FIG. 14 is an isometric view of an embodiment of the occluder of thepresent invention;

FIG. 15 is a side view of the occluder of FIGS. 11A-11C deployed invivo.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a device for occluding an aperture withinbody tissue. In particular and as described in detail below, theoccluder of the present invention may be used for closing an ASD or PFOin the atrial septum of a heart. Although the embodiments of theinvention are described with reference to an ASD or PFO, one skilled inthe art will recognize that the device and methods of the presentinvention may be used to treat other anatomical conditions. As such, theinvention should not be considered limited in applicability to anyparticular anatomical condition.

FIG. 1 illustrates a human heart 10, having a right atrium 11 and a leftatrium 13 and including various anatomical anomalies 18 a and 18 b. Theatrial septum 12 includes septum primum 14 and septum secundum 16. Theanatomy of the septum 12 varies widely within the population. In somepeople, septum primum 14 extends to and overlaps with septum secundum16. The septum primum 14 may be quite thin. When a PFO is present, bloodcould travel through the passage 18 a between septum primum 14 andseptum secundum 16 (referred to as “the PFO tunnel”). Additionally oralternatively, the presence of an ASD could permit blood to travelthrough an aperture in the septal tissue, such as that schematicallyillustrated by aperture 18 b.

In this application, “distal” refers to the direction away from acatheter insertion location and “proximal” refers to the directionnearer the insertion location.

The occluder 20 may be further varied by altering the cutting pattern ontube 25. For example, and as shown in FIGS. 2A, 2B-2D, and 3A-3C,petal-shaped loops 32 (FIGS. 2A-2D and FIG. 3A) are produced by cuttingslits 31 in the upper portion of tube 25 according to the cuttingpattern shown in FIG. 2A. As shown in FIG. 2B, tube 25 is cut in half toform half sections 91 a and 91 b. The half sections 91 a and 91 b arefurther cut to a proximal distance from end 39 into quarter sections 92a, 93 a, 92 b, and 93 b. The cuts are discontinued and quarter sections92 a and 93 a form half section 94 a at end 39, and quarter sections 92b and 93 form half section 94 b at end 39. Upon application of forceF_(d) to end 39, struts 32 bow and twist outward to form petal-shapedloops 32 in distal side 30, as shown in FIGS. 2C-2D. The movement of thestruts during deployment is such that the struts rotate in an orthogonalplane relative to the axis of the device. Central tube 22 may beconstrained during the application of force F_(d), or any combination offorces sufficient to reduce the axial length of the tube 25 may beapplied. One end of each of petal-shaped loops 32 originates fromcentral tube 22, while the other end originates from end 39 (FIGS. 2B-2Cand FIG. 3A). Petal-shaped loops 42 may be formed in proximal side 40,as shown in FIGS. 2B-2D, using the same cutting pattern described above.

Given that the surface of occluder 20 will contact septal tissue 12 onceit is deployed in vivo, slits 31 and 41 are further cut so as to preventthe formation of sharp, potentially damaging edges along their length.For example, a heated cutting tool may be used to cut slits 31 and 41such that the material of tube 25 melts slightly when placed in contactwith the cutting tool. Such melting rounds the edges of the sections.Lasers may also be used to cut slits 31 and 41. According to thisprocess, the edges of loops 32 formed by the cutting of slits 31 and 41are blunted (due to melting) to prevent tissue damage in vivo.

The tube(s) 25 forming occluder 20 includes a biocompatible metal orpolymer. In at least some embodiments, the occluder 20 is formed of abioresorbable polymer, or a shape memory polymer. Shape memory polymerscan be advantageous so that the structure of the device assists inpressing the PFO tunnel closed. In other embodiments, the occluder 20 isformed of a biocompatible metal, such as a shape memory alloy (e.g.,nitinol). The thermal shape memory and/or superelastic properties ofshape memory polymers and alloys permit the occluder 20 to resume andmaintain its intended shape in vivo despite being distorted during thedelivery process. Alternatively, or additionally, the occluder 20 may beformed of a bioresorbable metal, such as iron, magnesium, orcombinations of these and similar materials. The cross-sectional shapeof tube 25 may be circular or polygonal, for example square, orhexagonal. The slits 31 and 41 may be disposed on the face of thepolygon (i.e., the flat part) or on the intersection of the faces.

The tube can be extruded or constructed of a sheet of material androlled into a tube. The sheet of material could be a single ply sheet ormultiple ply. The slits that form the struts could be cut or stampedinto the tube prior to rolling the tube to connect the ends to form anenclosed cross section. Various geometrical cross sections are possibleincluding circular, square, hexagonal and octagonal and the joint couldbe at the vertex or along the flat of a wall if the cross section is ofa particular geometery. Various attachment techniques could be used tojoin the ends of the sheet to form a tube, including welding, heatadhesives, non-heat adhesives and other joining techniques suitable forin-vivo application.

The surface of tube 25 may be textured or smooth. An occluder 20 havinga rough surface produces an inflammatory response upon contact withseptal tissue 12 in vivo, thereby promoting faster tissue ingrowth,healing, and closure of aperture 18 a (shown in FIG. 1). Such a roughsurface may be produced, for example, by shaving tube 25 to producewhiskers along its surface. For example, central tube 22 may includesuch whiskers. Additionally or alternatively, the surface of tube 25 maybe porous to facilitate cell ingrowth.

The distal side 30 of the occluder 20 (also called the “anchor portion”)is shown in FIG. 2C and 2D. The distal side 30 includes four loops 32 a,32 b, 32 c, and 32 d (collectively referred to as loops 32). Aspreviously described, each of loops 32 a-32 d are formed bycorresponding struts 32 a-3 d produced by cutting slits 31. Theapplication of force F_(d) to end 39 of tube 25 brings the axial ends ofslits 31 together such that struts 32 bow and twist outwardly to formloops 32 of distal side 30 (FIGS. 2B-2C). Central tube 22 may beconstrained during the application of force F_(d). One skilled in theart will recognize that any combination of forces sufficient to reducethe axial length of the tube 25 would be sufficient to deploy the distalside 30 of occluder 20.

As illustrated, the loops 32 are evenly distributed about central tube22 and end 39. Thus, when proximal side 30 includes four loops 32 (asshown in FIGS. 2C and 2D), the four slits 31 are spaced 90 degreesapart. Similarly, when proximal side 30 includes six loops 32, the sixslits 31 are spaced 60 degrees apart. The angle between equally-spacedslits 31 in proximal side 30 is determined by the formula (360/n_(d)).

Although the distal side 30 of the occluder 20 shown in FIG. 3A includesfour loops 32, occluders according to the present invention may includeany number of loops 32 necessary for a given application. In particularembodiments, the distal side 30 of occluder 20 includes six loops (FIG.4A). Occluders having between four and ten loops 32 may be formedwithout requiring significant adjustments in the processes described inthis application. However, occluders having less than four or more thanten loops 32 may be complicated to manufacture and deliver through thevasculature.

Regardless of the number of loops included in distal side 30 anddepending upon the material used to form occluder 20, the outer shape ofloops 32 may vary. In at least some embodiments, the loops 32 arerounded to provide an occluder 20 having a smooth, circular perimeter.As the number of loops 32 in the distal side 30 of occluder 20increases, it becomes desirable to round the outer perimeters of theloops 32 so as to prevent the infliction of trauma on the surroundingseptal tissue 12.

The proximal side 40 of the occluder 20, shown in side view in FIG. 2D,also includes four loops, 42 a, 42 b, 42 c, and 42 d (collectivelyreferred to as loops 42). As previously described, each of loops 42 a-42d are formed by cutting slits 41. The application of force F_(p) to end44 of tube 25 brings the axial ends of slits 41 together such thatstruts 42 bow and twist outwardly to form loops 42 of proximal side 40(FIGS. 2C-2D). Central tube 22 may be constrained during the applicationof force F_(p). One skilled in the art will recognize that anycombination of forces sufficient to reduce the axial length of the tube25 would be sufficient to deploy the proximal side 40 of occluder 20. Asdescribed above for distal side 30, the loops 42 are evenly distributedabout central tube 22 and tip 44.

Although the proximal side 40 of the occluder 20 shown in FIG. 2Dincludes four loops 42, one skilled in the art will recognize that theproximal side 40 of an occluder according to the present invention mayinclude any number of loops 42 required and suitable for a givenapplication. In particular embodiments, the proximal side 40 of occluder20 includes six loops 42 (FIG. 4A). Further, although illustrated,distal side 30 and proximal side 40 both include four loops, there is norequirement that distal side 30 and proximal side 40 include the samenumber of loops. In fact, in particular applications, it may beadvantageous to use an occluder 20 in which distal side 30 containsfewer loops than proximal side 40, or vice versa.

In at least some embodiments, illustrated in FIGS. 4A and FIGS. 12A-12B,the loops 42 of the proximal side 40 are rotated with respect to theloops 32 of the distal side 30 to provide a better distribution offorces around the aperture 18 a. For example, proximal slits 41 may berotated such that they are offset from distal slits 31 by half the anglebetween adjacent slits on the distal side 30, e.g., when distal side 30and proximal side 40 of occluder 20 each have four loops 32 and 42,respectively, proximal slits 41 are rotated 30-45 degrees with respectto slits 31. Thus, in a preferred form, as shown in FIG. 12A, proximalslits 41 are rotated 45 degrees (as indicated by angle φ) with respectto distal slits 31. Correspondingly, as shown in FIG. 12B, proximalloops 42 are rotated 45 degrees with respect to distal loops 32 (asindicated by angle φ).

Further, loops 32 of distal side 30 may be bent to form concave loops,while loops 42 of proximal side 40 may be flat (FIG. 13). In thisembodiment, the outermost portions of loops 42 of proximal side 40oppose the outermost portions of the loops 32 of the proximal side 30,as described in more detail below, thereby creating a desirable opposingforce that secures the occluder 20 at its desired location in vivo. Soconfigured, the opposing compressive forces exerted by sides 30 and 40on the septal tissue 12 following deployment of occluder 20 in vivo isadvantageous in certain circumstances, such as closing certain kinds ofPFOs.

Whatever the number and shapes of loops 32 and 42, the loops 32 and 42may be of varied sizes to facilitate delivery of occluder 20, e.g. toimprove collapsibility of the occluder 20 or to enhance its securementat the delivery site. For example, loops 32 and 42 sized to betterconform with anatomical landmarks enhance securement of the occluder 20to the septal tissue 12 in vivo. As indicated above, the cross-sectionaldimensions of loops 32 and 42 are determined by the thickness of tube 25and the distance between adjacent slits 31 and 41. The length of slits31 and 41 determines the length of loops 32 and 42 and the radial extentof the deployed occluder 20. In at least some embodiments, each ofdistal side 30 and proximal side 40 has a diameter in the range of about10 mm to about 45 mm, with the particular diameter determined by thesize of the particular defect being treated. In particular embodiments,the diameter of distal side 30 will be different than that of proximalside 40 so as to better conform to the anatomy of the patient's heart.

The struts which form the loops may be constructed as illustrated inFIG. 2B. That is, about ⅓ the length of the slit is 91 a, ⅓ of thelength of the slit is the distance of 93 b and the final third of theslit is the length of 94 b. Of course other dimension would producedadvantageous results. In general, the longer the length of thehemispherical (as shown) struts, the stiffer the occluder will be. Thelonger the length of the quarter (as shown) struts, the less stiff theoccluder will be. In other words, the hemispherical cut (one of the two)may be 20-40 percent of the overall length of the cuts along the tube.Specifically, the hemispherical cuts could be 40% of the overall lengthand then the quarter cut be 20% of the cut. Also, the lengths of thehemispherical cuts need not be the same. It may be advantageous toshorten one or the other side of the hemispherical cut based on adesired stiffness characteristic for a particular application of theoccluder. In an alternative structure, the cuts can be extended in arange up to 100 percent of the length of one side of the occludingmember while still enabling the bow and twist of the struts.

As indicated previously and shown in FIGS. 2A and FIG. 2D, distal side30 and proximal side 40 of occluder 20 are connected by central tube 22.The central tube 22 is formed by that portion of tube 25 between theupper portion of tube 25, which contains slits 31, and the lower portionof tube 25, which contains slits 41. Given that the central portion oftube 25 remains uncut during the cutting process, the central portion ofthe tube maintains its profile upon the application of forces F_(d) andF_(p) and does not bow and twist outward as the proximal and distalsides are adapted to do.

Central tube 22 may be straight or positioned at an angle θ, as shown inFIG. 13. The type of central tube 22 included in a given occluder is, atleast in part, determined by the nature of the aperture 18. An occluderhaving a straight central tube 22 is particularly suited to treat ananatomical anomaly including a perpendicular aperture, such as an ASDand certain PFOs. Often, however, anatomical anomalies, such as certainPFOs, have non-perpendicular apertures and are sometimes quitesignificantly non-perpendicular. An occluder having an angled centraltube 22 is well-suited for treatment of such defects, such that theangle of the anatomical aperture 18 is more closely matched by thepre-formed angle θ of the occluder 20. Also, the length of the centertube should be varied depending on the anatomy of the defect beingclosed. Accordingly, the distal side 30 and proximal side 40 of occluder20 are more likely to be seated against and minimize distortion to theseptal tissue 12 surrounding the aperture 18, as shown in FIG. 15. Awell-seated occluder 20 is less likely to permit blood leakage betweenthe right 11 and left 13 atria, and the patient into which the occluder20 has been placed is, therefore, less likely to suffer embolisms andother adverse events. Advantageously, angled central tube 22 alsofacilitates delivery of occluder 20 because it is angled toward the endof the delivery sheath. In at least some embodiments, the angle θ isabout 0-45 degrees off the plane created by the proximal side 40.Proximal side 40 may bend depending upon, among other factors, thematerial used to form occluder 20. Accordingly, depending upon designconsiderations, tip 44 and end 39 may be aligned with central tube 22 orperpendicular to proximal side 40 or some variation in between. Oneskilled in the art will be capable of determining whether a straight orangled central tube 22 is best suited for treatment of a givenanatomical aperture 18 and the appropriate angle θ, typically in therange between 0 and 45 degrees or even to 90 degrees if used in anoblique passageway such as a very long tunnel PFO, for a given angledcentral tube 22. Further, one skilled in the art will recognize that theconcept of an angled central tube may be applied to septal occludersother than those disclosed herein.

When central tube 22 is positioned at angle θ, distal side 30 andproximal side 40 of occluder 20 may be configured such that they areeither directly opposing or, as shown in FIGS. 5B, 13 and 14, offset bydistance A. One skilled in the art will, of course, recognize that theshape and arrangement of either or both of distal side 30 and proximalside 40 may be adjusted such that the compressive forces they apply areas directly opposing as possible. However, in some clinicalapplications, an occluder 20 having an offset of distance A may beparticularly desirable. For example, as shown in FIGS. 13-14, if theseptal tissue 12 surrounding aperture 18 includes a disproportionatelythick portion (e.g. septum secundum 16 as compared to septum primum 14),the offset A may be used to seat occluder 20 more securely upon septaltissue 12. Moreover, the offset A allows each of sides 30 and 40 to becentered around each side of an asymmetric aperture 18.

When a central tube 22 at angle θ is included in occluder 20, a markeris required to properly orient the occluder 20 in its intended in vivodelivery location. For example, platinum wire may be wrapped around oneof loops 32 or 42 so as to permit visualization of the orientation ofthe occluder 20 using fluoroscopy. Alternatively, other types of markersmay be used, e.g. coatings, clips, etc. As one skilled in the art wouldappreciate, the radiopaque marker could be blended in with the extrudateand thus provide visibility under fluoroscopy. As will be readilyunderstood by one skilled in the art, the orientation of anon-symmetrical occluder 20 during delivery is of great importance. Ofcourse, when a non-symmetrical occluder 20 is used, the periphery of theoccluder 20 may be configured such that the clamping force applied bythe proximal side 40 is directly opposed to that applied by the distalside 30.

Upon deployment in vivo (a process described in detail below), anoccluder 20 according to the present invention applies a compressiveforce to the septal tissue 12. Distal side 30 is seated against theseptal tissue 12 in the left atrium 13; central tube 22 extends throughthe aperture 18; and proximal side 40 is seated against the septaltissue 12 in the right atrium 11. At least some portion of each of loops32 and 42 contacts septal tissue 12. In particular embodiments, asubstantial length of each of loops 32 and 42 contacts septal tissue 12.As illustrated in the representative Figures, the proximal side 40 anddistal side 30 of occluder 20 overlap significantly, such that theseptal tissue 12 is “sandwiched” between them once the occluder 20 isdeployed. According to at least some embodiments and depending upon thematerial used to form occluder 20, the loops 32 and 42 provide both aradially-extending compressive force and a circumferential compressiveforce to septal tissue 12. In these embodiments, the compressive forcesare more evenly and more widely distributed across the surface of theseptal tissue 12 surrounding the aperture 18 and, therefore, provide theoccluder 20 with superior dislodgement resistance as compared to priorart devices. As used in this application, “dislodgement resistance”refers to the ability of an occluder 20 to resist the tendency of theforce applied by the unequal pressures between the right 11 and left 13atria (i.e. the “dislodging force”) to separate the occluder 20 from theseptal tissue 12. Generally, a high dislodgement resistance isdesirable.

Loops 32 and 42 are also configured to minimize the trauma they inflicton the septal tissue 12 surrounding aperture 18. Specifically, asindicated previously, the outer perimeter of loops 32 and 42 may berounded. Accordingly, occluder 20 has a low compression resistance. Forexample, as illustrated in FIGS. 2B-2D, the circumferential portions ofloops 32 and 42 are thinner than the orthogonally-extending portions ofloops 32 and 42; therefore, the center of the occluder 20 is strongerthan its perimeter. As used in this application, “compressionresistance” refers to the ability of an occluder 20 to resist thelateral compressive force applied by the heart as it contracts during aheartbeat. Generally, an occluder that resists compressive force, i.e.has high compression resistance, is undesirable because its rigid shapeand arrangement may cause trauma to the septal tissue 12, the rightatrium 11, and/or the left atrium 13.

According to at least some embodiments of the present invention,occluder 20 further includes a catch system, generally indicated at 131,that secures the occluder 20 in its deployed state. The catch mechanism131, in general, maintains the shape and arrangement of occluder 20 oncethe occluder 20 has been deployed. Catch system 131 reduces andmaintains the axial length L of the occluder 20 so that occluder 20maintains its deployed state, is secured in the aperture 18, andconsistently applies a compressive force to septal tissue 12 that issufficient to close aperture 18. Catch system 131 is particularlyadvantageous when the occluder 20 is formed of a polymeric material, aspreviously described, because the polymeric occluder 20 may be deformedduring delivery such that it may not fully recover its intended shapeonce deployed. By reducing and maintaining the axial length L ofoccluder 20 once it has been deployed in vivo, catch mechanism 131compensates for any undesirable structural changes suffered by occluder20 during delivery. In some embodiments, catch system 131 includes aceramic material or a material selected from the group consisting ofmetals, shape memory materials, alloys, polymers, bioabsorbablepolymers, and combinations thereof. In particular embodiments, the catchsystem may include nitinol or a shape memory polymer. Further, the catchsystem may include a material selected from the group consistingTeflon-based materials, polyurethanes, metals, polyvinyl alcohol (PVA),extracellular matrix (ECM) or other bioengineered materials, syntheticbioabsorbable polymeric scaffolds, collagen, and combinations thereof.

Catch system 131 may take a variety of forms, non-limiting examples ofwhich are provided in FIGS. 6A-6E. For example, as shown in FIG. 6A,catch system 131 includes two members, e.g., balls, 133 and 135 attachedto delivery string 137. The catch system and catch element arepreferably the same material as the occluder, although based on designselection, they could be the same or different material. In certaincircumstances, it may be necessary to make them of different material.Delivery string 137 is permanently attached to member 135 and is thenthreaded through end 39, distal portion 30 of tube 25, central tube 22,proximal portion 40 of tube 25, and tip 44, such that ball 133 islocated between central tube 22 and end 39 and ball 135 is located onthe distal side of end 39. The function of catch system 131 is shown inFIGS. 6B-6E. Ball 133 is designed such that, upon the application ofsufficient pulling force F₁ to delivery string 137, it passes throughcentral tube 22 (FIG. 6B) and tip 44 (FIG. 6C). Ball 133 cannot reentertip 44 or central tube 22 without the application of a sufficient,additional force. In this manner, ball 133 may be used to bring togetherthe distal side 30 and the proximal side 40, thereby reducing andmaintaining the axial length L of occluder 20. Obviously, during theapplication of pulling force F₁, the tip 44 of occluder 20 must be heldagainst an object, such as a delivery sheath. Ball 135 is designed suchthat, upon application of sufficient pulling force F₂ to delivery string137, it passes through end 39 (FIG. 6D) and central tube 22 (FIG. 6E).The pulling force F₂ required to move ball 135 through end 39 andcentral tube 22 is greater than the pulling force F₁ required to moveball 133 through central tube 22 and tip 44. However, ball 135 cannotpass through tip 44. Thus, the application of sufficient pulling forceF₂ to ball 135 releases distal side 30 and proximal side 40, asdescribed in more detail below. It should be noted that while members133 and 135 are illustrated as spherical members in FIGS. 6A-6E, members133 and 135 may take any suitable shape. For example, members 133 and135 may be conical. The narrow portions of conical members 133 and 135point toward tip 44 of proximal side 40. One possible mode of recoveryor retrieval for this device is simply reversing the implantationprocedure. Of course, other modes of recovery or retrieval are possible,some of which are described in this specification.

A different system for securing the device in the deployed state isshown in FIGS. 7A-7C. A locking mechanism 191 includes a hollow cylinder141 having at least two half-arrows 143 and 145 located at its proximalend (FIG. 7A). Cylinder 141 enters tip 44 under application of pullingforce F₁ to delivery string 137. As cylinder 141 enters tip 44,half-arrows 143 and 145 are forced together such that the diameter ofthe proximal end of cylinder 141 is reduced (FIG. 7B). Under continuedapplication of pulling force F₁, half-arrows 143 and 145 pass throughtip 44 and expand to their original shape and arrangement (FIG. 7C).Given that half-arrows 143 and 145 extend beyond the diameter of tip 44,the axial length of an occluder 20 including the locking mechanism 191shown in FIGS. 7A-7C is maintained in its reduced state. If the implantneeds to be removed or repositioned, the locking mechanism 191 shown inFIGS. 7A-7C may be released by moving half-arrows 143 and 145 togethersuch that the diameter of the proximal end of cylinder 141 is smallerthan that of tip 44 and cylinder 141 passes through tip 44. Cylinder 141may then be withdrawn from tip 44.

One skilled in the art will recognize that catch system 131 may assumenumerous configurations while retaining its capability to reduce andmaintain the axial length L of occluder 20 such that occluder 20maintains its deployed state. For example, catch system 131 may includea threaded screw, a tie-wrap, or a combination of catch systems 131.Furthermore, catch system 131 may include multiple members that mayprovides a stepped deployment process. For example, catch system 131 asdepicted in FIGS. 6A-6E may include three balls. In this configuration,one ball is used to secure the distal end 30 of occluder 20 and anotherball is used to secure the proximal end 40 of occluder 20, and the thirdball is secured to the distal end. Any suitable catch system 131 may beincorporated into any of the embodiments of occluder 20 describedherein. One skilled in the art will be capable of selecting the catchsystem 131 suitable for use in a given clinical application.

Occluder 20 may be modified in various ways. According to someembodiments of the present invention, distal side 30 and/or proximal 40side of occluder 20 may include a tissue scaffold. The tissue scaffoldensures more complete coverage of aperture 18 and promotes encapsulationand endothelialization of septal tissue 12, thereby further encouraginganatomical closure of the septal tissue 12. The tissue scaffold may beformed of any flexible, biocompatible material capable of promotingtissue growth, including but not limited to polyester fabrics,Teflon-based materials, ePTFE, polyurethanes, metallic materials,polyvinyl alcohol (PVA), extracellular matrix (ECM) or otherbioengineered materials, synthetic bioabsorbable polymeric scaffolds,other natural materials (e.g. collagen), or combinations of theforegoing materials. For example, the tissue scaffold may be formed of athin metallic film or foil, e.g. a nitinol film or foil, as described inU.S. Patent Appl. No. 2003/0059640 (the entirety of which isincorporated herein by reference). In those embodiments where occluder20 includes a tissue scaffold, the scaffold may be located on theoutside the face of distal side 30 with an alternative of includingscaffold also inside the proximal side 40. Also, the tissue scaffoldcould be disposed against the tissue that is sought to be occluded, suchas the septal tissue 12 so that the proximity of the tissue scaffold andseptal tissue 12 promotes endothelialization. Loops 32 and 42 may alsobe stitched to the tissue scaffold to securely fasten the scaffold tooccluder 20. One skilled in the art will be able to determine thoseclinical applications in which the use of tissue scaffolds and/orstitches is appropriate.

Occluder 20 may be further modified so that it lacks end 39 and tip 44,as shown in FIGS. 8A-8C, and, therefore, has a reduced septal profile.Such an occluder may be formed in several ways. For example, accordingto one embodiment, slits 31 and 41 are extended through end 39 and tip44, respectively, of tube 25 during the cutting process. This cuttingpattern produces struts 32 that deform during deployment to produceincomplete loops 32. One side of the device, facing the viewer as shownin FIG. 8A, is formed by slits 31 that extend along the tube 25 tovarying lengths. The tube 25 is cut in half to form half sections 154 aand 154 b. The half sections 154 a and 154 b are further cut to aproximal distance from the end 39 into quarter sections 155 a, 156 a,155 b, and 156 b. The ends of the quarter sections 155 a and 155 b arejoined at “free ends” 153 to close the loop 32. Similarly, the free endsof quarter sections 156 a and 156 b may be joined by appropriatecutting, see FIG. 8 b. The ends may be joined using any suitableconnectors, e.g., 151, e.g., welds. One of skill in the art willrecognize that the free ends 153 of loops 32 may be connected usingother means, including but not limited to seams and bonds obtained byheat or vibration.

In the above embodiment, the slits in the quarter sections are runcompletely through the end of the tube 39. In an alternative embodiment,the end 39 may remain uncut, thereby eliminating the need for a weld tojoin the quarter sections together.

The embodiment illustrated in FIGS. 8A-8C depicts an occluder 20 inwhich both sides are formed according to the above-described design.Alternatively, an occluder 20 according to the present invention mayinclude a hybrid structure, wherein one side is designed according tothe embodiment shown in FIGS. 8A-8C and the other side is designedaccording to other types of structures disclosed in this application.

Occluder 20 may be prepared for delivery to an aperture 18 in any one ofseveral ways. Slits 31 and 41 may be cut such that tube 25 bends intoits intended configuration following deployment in vivo. Specifically,slits 31 and 41 may be cut to produce struts 32 and 42 of a thicknessthat facilitates the bending and formation of loops 32 and 42 upon theapplication of forces F_(d) and F_(p) during deployment. Alternativelyand/or additionally, a tube 25 formed of a shape memory material may bepreformed into its intended configuration ex vivo so that it willrecover its preformed shape once deployed in vivo. According to at leastsome embodiments, this preforming technique produces more reliabledeployment and bending of occluder 20 in vivo. An intermediate approachmay also be used: tube 25 may be only slightly preformed ex vivo suchthat it is predisposed to bend into its intended shape in vivo uponapplication of forces F_(d) and F_(p).

An occluder 20 as described herein may be delivered to an anatomicalaperture 18 using any suitable delivery technique. For example, distalside 30 and proximal side 40 of occluder 20 may be deployed in separatesteps, or both distal side 30 and proximal side 40 of occluder 20 may bedeployed prior to engaging the catch system. One delivery method will bedescribed in detail herein. As shown in FIGS. 9A-9H, a delivery sheath161 containing pusher sleeve 169 (shown in FIG. 9H) is used to deliveroccluder 20 including the catch system 131 illustrated in FIGS. 6A-6E.Sheath 161 contains occluder 20 in its elongated, delivery form (FIG.9A). As shown in FIG. 9B, delivery sheath 161 is first inserted into theright atrium 11 of the patient's heart. Sheath 161 is next insertedthrough aperture 18 located in the septal tissue 12 (which, in thisexample, is a PFO tunnel) and into the left atrium 13 (FIG. 9C). Distalside 30 of occluder 20 is then deployed into the left atrium 13, asshown in FIG. 9D. Following deployment of distal side 30, pulling forceF₁ is applied to delivery string 137 such that ball 133 passes throughthe central tube 22, thereby securing distal side 30 into its deployedstate (FIG. 9E). Sheath 161 is withdrawn through the aperture 18 andinto the right atrium 11, such that central tube 22 is deployed throughthe aperture 18 (FIG. 9F). Proximal side 40 of occluder 20 is thendeployed into the right atrium 11 (FIG. 9G), and pulling force F₁ isagain applied to delivery string 137 such that ball 133 passes throughtip 44, thereby securing the proximal side 40 into its deployed state(FIG. 9H). When properly deployed, occluder 20 rests within the aperture18, and the distal side 30 and proximal side 40 exert a compressiveforce against septum primum 14 and septum secundum 16 in the left 13 andright 11 atria, respectively, to close the aperture 18, i.e. the PFO.When occluder 20 is properly deployed, delivery string 137 is detachedfrom catch system 131, including balls 133 and 135 and a connectingmember, and sheath 161 is then withdrawn from the heart. In the eventoccluder 20 is not properly deployed after performing the proceduredescribed above, the occluder 20 may be recovered by reversing the stepsof the delivery sequence.

In the an alternative recovery technique, the occluder 20 may berecovered and repositioned by catch system 131 as shown in FIGS.10A-10D. Pusher sleeve 169 in sheath 161 is positioned against tip 44 inthe right atrium 11 (FIG. 10A). Pulling force F₂ is applied to deliverystring 137, such that ball 135 passes through end 39 and into centraltube 22, thereby releasing distal side 30 from its deployed state (FIG.10B). Force F₂ is again applied to delivery string 137 so that ball 135subsequently passes through central tube 22, thereby releasing proximalside 40 from its deployed state (FIG. 10C). Delivery string 137 is thenpulled further such that occluder 20, now in its elongated state, isretracted into sheath 161 (FIG. 10D). Following recovery of occluder 20,sheath 161 may be withdrawn from the heart and another occluder insertedin the desired delivery location as described above and shown in FIGS.9A-9H.

Distal side 30 and proximal side 40 are connected by central tube 22. Asillustrated, the central tube 22 is an uncut central part of the tubeused to form occluder 20. As described below, the entire tube isindicated by reference numeral 25. As shown, the occluder 20 may beinserted into the septal tissue 12 to prevent the flow of blood throughthe aperture 18 a, e.g., the occluder may extend through the PFO tunnelsuch that the distal side 30 is located in the left atrium 13 and theproximal side 40 is located in the right atrium 11. Additionally oralternatively, the occluder 20 may be inserted into the septal tissue 12so as to prevent the flow of blood through the aperture 18 b, e.g., theoccluder may extend through the ASD such that the distal side 30 islocated in the left atrium 13 and the proximal side 40 is located in theright atrium 11. As used in this application, unless otherwiseindicated, the term “aperture 18” refers to any anatomical anomaly thatmay be treated by use of occluder 20, such as PFO 18 a or ASD 18 b.

The occluder 20 is constructed of one or more metal or polymer tube(s),referred to collectively as “tube” 25. Tube 25 includes slits 31 and 41,which are formed using an etching or cutting process that produces aparticular cutting pattern on tube 25. For example, as shown in FIG.11C, slits 31 are cut along the axial length of the upper half of tube25 using a cutting tool, e.g., a razor blade. According to someembodiments of the present invention and as shown in FIG. 11C, slits 31are cut without removing any significant amount of material from tube25, i.e., the formation of slits 31 does not significantly reduce theoverall volume of tube 25. According to other embodiments of the presentinvention, slits 31 are formed by cutting material out of tube 25 suchthat the volume of tube 25 is reduced. Both ends of each of slits 31 arerounded so as to relieve stresses at the axial ends of the slits 31.This prevents slits 31 from lengthening due to cyclic stresses presentin a beating heart and the resultant material fatigue. In thoseembodiments where slits 31 are cut without removing any significantamount of material from tube 25, rounded ends or holes 33 may beproduced by burning holes at both ends of each of slits 31. In thoseembodiments where slits 31 are formed by cutting material out of tube25, rounded ends 33 may be formed during the cutting process. The sizeof rounded ends 33 may vary depending upon the dimensions of tube 25 andthe amount of stress release required by the deformation.

As shown in FIGS. 11A-11C, cutting slits 31 forms struts 32 in tube 25.Upon deployment, struts 32 deform into a shape generally characterizedas “loops” 32. Thus, the number of slits 31 cut in the upper half oftube 25 according to the foregoing process is n_(d), where n_(d) is thenumber of loops 32 ultimately desired in distal side 30 when occluder 20is deployed. Thus, four slits 31 are cut in the upper portion of tube 25to produce four struts 32 a, 32 b, 32 c, and 32 d (FIGS. 11A-11C).

Upon the application of force F_(d) to distal end 39 of tube 25, theaxial ends of slits 31 are brought together such that struts 32 bowradially outwardly to form loops 32 of distal side 30. Central tube 22may be constrained during the application of force F_(d). One skilled inthe art will recognize that any combination of forces sufficient toreduce the axial length of the tube 25 would be sufficient to deploy thedistal side 30 of occluder 20. The cross-sectional dimensions of loops32 are determined by the thickness of tube 25 and the distance betweenadjacent slits 31. The length of slits 31 determines the length of loops32 and the radial extent of the deployed occluder 20. In this manner,the dimensions of loops 32 may be controlled during production ofoccluder 20. For example, as more material is removed from tube 25during the cutting process used to form slits 31, the thickness of loops32 decreases. Moreover, any or all of slits 31 may be cut such thatstruts 32 vary in thickness along their length; accordingly, loops 32will also vary in thickness along their length. In some embodiments, itmay be desirable to have a wider strut 32 at the location where it joinstube 25 to create a sturdier device. Alternatively, it may be desirableto have a wider portion elsewhere along strut 32 such that occluder 20is predisposed to bend into a certain shape and arrangement. Forexample, the portion of each of struts 32 nearer central tube 22 may bethinner than the portion of each of struts 32 nearer end 39 tofacilitate bending of struts 32 into loops 32 during deployment ofoccluder 20.

Loops 42 in proximal side 40 of occluder 20 are produced by formingslits 41 in the lower half of tube 25 using the same cutting process(es)described above for distal side 30 (FIG. 11B). The cutting of slits 41produces struts 41 in tube 25 (FIGS. 11A-11B) that deform into loops 42in proximal side 40 when occluder 20 is deployed. The number of slits 41cut in the lower half of tube 25 is n_(p), where n_(p) is the number ofloops 42 ultimately desired in proximal side 40 of occluder 20. Thus,four slits 41 are cut in the upper portion of tube 25 to produce fourstruts 42 a, 42 b, 42 c, and 42 d and, ultimately, four loops 42 a, 42b, 42 c, and 42 d in proximal side 40. Although distal side 30 andproximal side 40 may each include the same number of loops 32 and 42,respectively, there is no requirement that the number of loops 32 isidentical to the number of loops 42, as described in more detail below.When force F_(p) is applied to end 44 of tube 25, the axial ends ofslits 41 are brought together such that struts 42 bow radially outwardlyto form loops 42 of proximal side 40. As discussed above in the contextof deploying distal side 30, central tube 22 may be constrained duringthe application of force F_(p). One skilled in the art will recognizethat any combination of forces sufficient to reduce the axial length ofthe tube 25 would be sufficient to deploy the proximal side 40 ofoccluder 20. The dimensions of loops 42 may be varied as described abovefor loops 32.

Slits 31 and 41, as shown in FIG. 11B, are cut axially along the lengthof tube 25. However, as one of skill in the art will recognize, slits 31and/or 41 may also be cut along other dimensions of tube 25. Forexample, as shown in FIG. 11A, slits 31 and 41 may be cut at an anglesuch that they are helically disposed on tube 25. Angled slits 31 and 41produce angled struts 32 and 42, which deform into angled loops 32 and42 during deployment. Further, slits 31 and 41 need not be straight; forexample, slits 31 and 41 may be cut as zigzags, S-shaped slits, orC-shaped slits. One skilled in the art will be capable of selecting theangle for the slits 31 and/or 41 and the loop 32 and 42 shape(s)appropriate for a given clinical application. For example, when occluder20 is formed from a polymer tube 25, straight loops 32 and 42 may bepreferable because they will impart maximum stiffness to occluder 20. Ifthe tube 25 is formed of a stiffer material, the angled slits 31 and/or41 may provide a more desired stiffness to the occluder 20.

One skilled in the art will recognize that the occluders describedherein may be used with anti-thrombogenic compounds, including but notlimited to heparin and peptides, to reduce thrombogenicity of theoccluder and/or to enhance the healing response of the septal tissue 12following deployment of the occluder in vivo. Similarly, the occludersdescribed herein may be used to deliver other drugs or pharmaceuticalagents (e.g. growth factors, peptides). The anti-thrombogenic compounds,drugs, and/or pharmaceutical agents may be included in the occluders ofthe present invention in several ways, including by incorporation intothe tissue scaffold, as previously described, or as a coating, e.g. apolymeric coating, on the tube(s) 25 forming the distal side 30 andproximal side 40 of the occluder 20. Furthermore, the occludersdescribed herein may include cells that have been seeded within thetissue scaffold or coated upon the tube(s) 25 forming the distal side 30and proximal side 40 of the occluder 20.

One skilled in the art will further recognize that occluders accordingto this invention could be used to occlude other vascular andnon-vascular openings. For example, the device could be inserted into aleft atrial appendage or other tunnels or tubular openings within thebody.

Having described preferred embodiments of the invention, it should beapparent that various modifications may be made without departing fromthe spirit and scope of the invention, which is defined in the claimsbelow.

1-45. (canceled)
 46. A septal defect occluder, comprising: an elongatebody having a longitudinal axis, a first end, a second end, and amid-point located between the first end and the second end; a firstcompressible side located adjacent to the first end, wherein the firstside includes at least two slits that extend generally parallel to thelongitudinal axis from a common first start location adjacent to thefirst end to a common first end location adjacent to the mid-point; asecond compressible side located adjacent to the second end, wherein thesecond side includes at least two slits that extend generally parallelto the longitudinal axis from a common second start location adjacent tothe mid-point to a common second end location adjacent to the secondend; wherein compression of the first side forms a first strut thatextends axially from both the first start location and the first endlocation, includes a curved member that extends generally parallel tothe longitudinal axis, and includes a first bend; and whereincompression the second side forms a second strut that extends axiallyfrom both the second start location and the second end location, andincludes a second bend.
 47. The septal defect occluder of claim 46,wherein the curved member is substantially concave.
 48. The septaldefect occluder of claim 46, wherein the first strut and the secondstrut extend axially from the elongate body at angles of less than 90degrees from the longitudinal axis.
 49. The septal defect occluder ofclaim 48, wherein the angles are less than about 45 degrees from thelongitudinal axis.
 50. The septal defect occluder of claim 48, whereinthe first bend is axially offset from the second bend.
 51. The septaldefect occluder of claim 46, wherein the first strut includes anoutermost portion that directly opposes an outermost portion of thesecond strut.
 52. The septal defect occluder of claim 46, wherein thesecond strut includes a curved member that extends generally parallel tothe longitudinal axis.
 53. The septal defect occluder of claim 46,wherein the first strut is rotated about the longitudinal axis by lessthan approximately 45 degrees with respect to the second strut.
 54. Theseptal defect occluder of claim 46, wherein the first bend is locatedcloser to the first end location than to the first start location. 55.The septal defect occluder of claim 46, wherein the second bend islocated closer to the second start location than to the second endlocation.
 56. The septal defect occluder of claim 46, wherein the firststrut and the second strut are formed without rotation about thelongitudinal axis of the first end relative to the second end.
 57. Aseptal defect occluder, comprising: an elongate body having alongitudinal axis, a first end, a second end, and a mid-point locatedbetween the first end and the second end; a first compressible sidelocated adjacent to the first end, wherein the first side includes atleast two slits that extend generally parallel to the longitudinal axisand forms a first strut when the first side is compressed, wherein thefirst strut remains generally parallel to the longitudinal axis as thefirst strut extends axially from the elongate body, the first strutincluding two curved members and a bend located therebetween; and asecond compressible side located adjacent to the second end, wherein thesecond side includes at least two slits that extend generally parallelto the longitudinal axis and forms a second strut when the second sideis compressed, wherein the second strut remains generally parallel tothe longitudinal axis as the second strut extends axially from theelongate body, the second strut including two members and a bend locatedtherebetween.
 58. The septal defect occluder of claim 57, wherein thetwo curved members are substantially concave.
 59. The septal defectoccluder of claim 57, wherein the first strut and the second strutextend axially from the elongate body at angles of less than 90 degreesfrom the longitudinal axis.
 60. The septal defect occluder of claim 59,wherein the angles are less than about 45 degrees with respect to thelongitudinal axis.
 61. The septal defect occluder of claim 57, whereinthe bend of the first strut is axially offset from the bend of thesecond strut.
 62. The septal defect occluder of claim 57, wherein thebend of the first strut is located closer to the mid-point than to thefirst end.
 63. The septal defect occluder of claim 57, wherein the bendof the second strut is located closer to the mid-point than to thesecond end.
 64. The septal defect occluder of claim 57, wherein thefirst strut is rotated about the longitudinal axis by less thanapproximately 45 degrees with respect to the second strut.
 65. Theseptal defect occluder of claim 57, wherein the two members of thesecond strut are curved.